The present disclosure herein relates to semiconductor devices and, more particularly, to semiconductor devices including static random access memory (SRAM) cells.
Semiconductor devices are widely used in various industrial areas such as electronic systems, automobiles and/or vessels because of small size, multi-function and/or low fabrication cost thereof. Semiconductor devices include semiconductor memory devices storing logic data, semiconductor logic devices processing operations of logical data, and hybrid semiconductor devices having both memory and logic functions. Semiconductor logic devices may include logic circuits performing logical operations and semiconductor memory cells storing data used in the logical operations.
Semiconductor memory cells may be categorized as either nonvolatile memory cells or volatile memory cells. Nonvolatile memory cells typically retain stored data even when their power supplies are interrupted. Nonvolatile memory cells may include flash memory cells, phase change memory cells and magnetic memory cells.
In contrast, volatile memory cells typically lose their stored data when their power supplies are interrupted. Volatile memory cells may include dynamic random access memory (DRAM) cells and SRAM cells. SRAM cells typically are capable of greater operational speeds than DRAM cells. Further, while DRAM cells typically require periodical data refreshing by rewriting data to the memory, SRAM cells typically do not require refreshing. Because of these characteristics of SRAM cells, some electronic systems such as portable devices still employ SRAM cells.
However, a typical SRAM cell may occupy a significantly greater area than a typical DRAM cell. Thus, compact SRAM cells have been developed to increase the level of integration density of semiconductor devices including such SRAM cells. There is also an ongoing demand for high performance SRAM cells.